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\ Practical Guide to Feline Dermatology

Diagnosis

The diagnosis is based on finding these 6-legged, orange-coloured larvae, either with the naked eye or with a magnifying glass. They can be identified on microscopical examination (Table 3:1) (Fig. 3 : f). Be wamed, these larvae are not always present at the time of consultation ^u.

Treatment

Treatment is difficult and reąuires repeated application of acaricide.

Fipronil** spray, 0.25%, applied monthly to the whole body, is moderately effective in the cat". However, increasing the freąuency (twice weekly) of spraying in larval predilection sites leads to much better efficacy (E. Guaguere, personal observations, 1998).

Treating the external environment is possible but disappointing. Clearing out gardens and vegetation along with pesticide sprays is strongly advised '.

Demodicosis

Aetiopathogenesis

Feline demodicosis is caused by the excessive proliferation of 2 species of mite from the family Demodicidae: Demodex cati, a resident of pilo-sebaceous units³ and Demodex gatoi, a shorter mite that lives in the superficial layers of the epidermis ¹² (Table 3:1). Their life cycle and modę of transmission are not well understood. Age does not seem to be a predisposing factor, although the “juvenile” form, seen in cats of less than 3 years, carries a better prognosis than the condition reported in cats older than 5 years, which is often associated with an underlying illness ^W3. Examples of underlying illnesses include FeLV and FIV infection, diabetes mellitus, hyperadrenocorticism, systemie lupus erythematosus and multicentric sąuamous celi carcinoma in situ ^U3'¹⁴. Siamese and Burmese breeds seem to be predisposed³.

Clinical features

The head and neck are the main areas affected, morę rarely the trunk and limbs. Skin lesions are characterised by erythema, papules or pustules, localised or diffuse hair loss, scaling, erosions, uleerations, crusting, comedones and hyperpigmentation ^u3 (Figs 3 : 17-21). In the Persian cat, a particular clinical form (greasy facial seborrhoea) has been observed ¹³ (Fig. 3 : 22). Bilateral erythemato-ceruminous otitis is often seen and may be the only clinical manifestation ¹¹³ (Fig. 3 : 23). Pruritus is variable but morę common with Demodex gatoi infestation.

Diagnosis

Deep skin scrapings can be used to demonstrate Demodex cati and Demodex gatoi in different stages of their life cycles¹³ (Table 3:1) (Figs 3 : g,h).

The possibility of an underlying disease must be investigated, especially when the condition is generalised ^U3,14.

Prognosis and treatment

The prognosis depends on the clinical form (the localised condition carries a better prognosis than the generalised form) and the underlying illness^{l l314}. The localised form can sometimes spontaneously resolve.

Amitraz* (0.25%o solution) can be given every 5 days for 4 - 6 weeks, following local washing with a keratolytic shampoo ^u3. This treatment is well tolerated.

Antiparasitic macrocyclic lactones (ivermectin*, milbemycin*) could be used here.

Control of the underlying illness must be instituted once the condition has been identified ^,314.

* This product is not licensed for use in the cat and responsibility for its use falls on the prescribing veterinary surgeon.

** This product is not licensed for this indication in the cat and responsibility for its use falls on the prescribing veterinary surgeon.

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